<!DOCTYPE html>
<html lang='en'>
<head>
    <meta charset='UTF-8'>
    <meta http-equiv='X-UA-Compatible' content='IE=edge'>
    <meta name='viewport' content='width=device-width, initial-scale=1.0'>
    <title>Document</title>
    <script src='../vue.js'></script>
</head>
<body>
    <div id='app'>
        <button @click="ishot=!ishot">改变天气</button>
        <h1>今天天气真{{ishot?'热':'冷'}}</h1>
        <img :src="url" alt="">
    </div>
    <script>
        Vue.config.productionTip = false;
        const vm = new Vue({
            el:'#app',
            data(){
                return {
                ishot:true,
                url:'./re.webp'
            }
            },
            watch:{
                //监听ishot属性
                ishot:{
                    //当被监听的ishot发生改变的时候,handle函数就会执行
                    handler(newValue,oldValue){
                        console.log(newValue,oldValue,'hand');

                        //根据当前的值 去修改url的地址
                        this.url = newValue?'./re.webp':'./leng.gif'
                    }
                }
            }
    })
    </script>
</body>
</html>